Hello, anyone got any experience with First Watt SIT2 used as a headphone amplifier?

I'm particularly interested in headphones like Utopia or HE1000v2, but any experience is welcomed. And I'm also interested in having experience re direct driving the SIT2 with a DAC or using a preamplifier.

thanks for your reply.
can you elaborate on the "sensitive" point please? you mean power or hum/noise?
if I understood correctly, power goes down with higher load, so the 10W at 8 ohm of the SIT2 should be much less on HE1000 or Utopia, right? maybe I got it wrong though.....

Both noise and power. SIT-2 has 100uV noise. For the Utopia this translates to 35dB noise based on 104db/mW and 80 ohm impedance. 35dB is still low, but you can do better. Based on 8ohm power output it would translate to 1000mW into 80 ohms. Super overkill for 104db/mw.

Speaker amps only start to make sense with really low sensitivity (HE-6) or really high impedance (600 ohms, e-stats)

Hello, anyone got any experience with First Watt SIT2 used as a headphone amplifier?

I'm particularly interested in headphones like Utopia or HE1000v2, but any experience is welcomed. And I'm also interested in having experience re direct driving the SIT2 with a DAC or using a preamplifier.

thanks and regards
mike

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Hi Mike,

Did you ever try a SIT-2 with headphones or were you enquiring in order to consider buying one?

I've just seen this thread as I have a SIT2 myself and I was going to try it with my HD800's to see how it sounds.

I have already tried my valve amps with the HD800's and they (2A3 and 300B SET amps) do sound great. Actually better than my dedicated headphone amps I have and tried (ca. $1000 level). But its the lack of convenience that puts me off between using speakers and headphones with the same amp!

I use a couple of different multibit DAC's in this set up including a custom Discrete DAC and a Yggdrasil. These are connected to the amps via a TVC. I'd never use digital volume control from the streaming source as that degrades the SQ too much.

Hi Jonathan,
I've used some of my cans, for example HE6 and HEK, with some loudspeakers amplifiers, for example Pass and Spectral, but I never used the SIT2, that's why my post. I never tried the Utopia with a loudspeaker amplifier, and actually the noise problem pointed above by Cspirou could be something concerning.
I also happen to have a TVC, a Promitheus with silver transformers, but I prefer to use my Aesthetix Calypso or my Spectral 30SL G2 since I find them much more vivid and dynamic. In some cases I also use the digital volume on my Vega dac, if used with a grain of salt (i.e. not too large attenuation) it is working nicely.
rgrds
mike

Hi Jonathan,
I've used some of my cans, for example HE6 and HEK, with some loudspeakers amplifiers, for example Pass and Spectral, but I never used the SIT2, that's why my post. I never tried the Utopia with a loudspeaker amplifier, and actually the noise problem pointed above by Cspirou could be something concerning.
I also happen to have a TVC, a Promitheus with silver transformers, but I prefer to use my Aesthetix Calypso or my Spectral 30SL G2 since I find them much more vivid and dynamic. In some cases I also use the digital volume on my Vega dac, if used with a grain of salt (i.e. not too large attenuation) it is working nicely.
rgrds
mike

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Thanks for the update. I'll post further once I get to try my headphones on the SIT2 then. I can't imagine that noise level is going to be detectable, but we'll see. I'm sure the "measurement crowd" could find plenty of amps which measure better than the SIT2, but it does sound wonderful on high efficiency speakers!

I've found that if the DAC has a decent output stage then sound quality is better with the TVC (Music First and Tribute TX's) than any active pre I've tried. As you're just adding another active stage to with its own signature or colourations.

SITs a.k.a. VFETs are super rare out-of-production unobtanium parts (I guess that Nelson has a stash) and not the same as regular JFETs as used in Schiit gear, etc.

Edit: I think the SIT-2 might be the only current production model using VFETs. You can get hold of vintage Sony and Yamaha B2 for instance which were mostly if not all Nelson Pass designs too. I really doubt any dedicated headphone amp exists which uses VFET transistors.

The SIT-2 is no longer in production. The SIT-3, using Nelson's new DEFiSIT technology (resisters removed, since it adds degeneration) is starting to come into production now to finish up the last of his SITs. These have less distortion, are harder to make, and as a bonus Nelson also lowered the price from $5K to $4K. IMHO this is the one you want, not the SIT-2. There is also a new version of the Sony VFET amp designed by Nelson that's coming out soon. Read more from Nelson himself here:

Personally I have an SIT-3 coming in for exclusive headphone use. I also have a Pass Labs XA25 and First Watt F7. I have another friend who has the SIT-2, and the background is pitch black with his Audeze headphones. That also echoes my experience with XA25 and F7- Pass Labs makes extremely quiet speaker amps, and are a great match for headphone use.

I've been using my SIT-2 with headphones for a little while now, see below for more.

Jelt2359 you're right that the SIT-2 is not in production any more. I'm guessing the OP was assuming that he'd find one used if it got a strong recommendation for headphone use. I'm willing to bet that the SIT-3 is not going to be much of a step forward in absolute SQ over the SIT-2. At least not for headphone use or for what I (and Nelson Pass himself!) use which is to drive high efficiency full range speakers (actually mine is mid / treble in a front horn). The SIT-3 does have better noise performance of course, higher output capability, higher damping factor, but as I say for my use that's not likely to be of much benefit. However, I will still buy a SIT-3 too anyway, as I could do with another couple of channels of HQ amplification, and these are less hassle than using valve amps in the long term. So I will see how they sound side by side myself.

The SIT-2 is indeed extremely quiet in use with my HD800's, to my ears it doesn't need any improvement in this area at all. Obviously with less efficient headphones this might be different, I only have HD800's and some older lesser dynamic ones.

The overall sound quality though with the SIT-2 is truly superb. It better's all my other dedicated headphone amps (a Cavalli, a Heron 5, a maxxed out BH Crack) by a significant margin. It sounds better than my Single Ended Tride amps too (3 high end all valve SET's a 45, a 2A3 and a 300B amp all mono block, with separate power supplies). Whilst the SIT-2 retains the SET "magic" on headphones as it does on speakers, it adds a solidity to the overall soundstage and imaging, as well as better bass depth and definition, and a really well extended sweet treble. The midrange on voice is as lovely as my 300B which is usually king in this area.

I'd love to hear a really high end all valve headphone amp in comparison to the SIT-2, as I can't imagine many other amps could get close to it. I'm thinking of a TOTL Eddie Current, DNA, EAR, or Apex amp. So if there's anyone in the South of the UK that fancies a listening session and has one of these, please let me know and I'd love to arrange it.

many thanks to everyone for the precious infos.
I should be able to audition the SIT-2 with my Utopia, lt's see.... emh.... hear the result. If as I imagine it wil be nice, I'll buy an used SIT-2 or a new SIT-3

I'd love to hear a really high end all valve headphone amp in comparison to the SIT-2, as I can't imagine many other amps could get close to it. I'm thinking of a TOTL Eddie Current, DNA, EAR, or Apex amp. So if there's anyone in the South of the UK that fancies a listening session and has one of these, please let me know and I'd love to arrange it.

Kind regards,

Jonathan ​

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Hi Jonathan. I have an Angstrom Stella here for the time being (a stupid expensive tube headphone amp which is actually really really good imho). Also have a First Watt F7 that I use with my headphones...and I'm in the south (ish) of the UK. Send me a pm if you'd like to arrange a listen.

Hi Jonathan. I have an Angstrom Stella here for the time being (a stupid expensive tube headphone amp which is actually really really good imho). Also have a First Watt F7 that I use with my headphones...and I'm in the south (ish) of the UK. Send me a pm if you'd like to arrange a listen.

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Hi pedalhead, I will pm you, many thanks. That Anstrom amp looks good, and you're right, if its anything like the integrated amp I saw, definitely in the stupid expensive bracket!

by the way... am I wrong in saying that the SIT used by Pass are somewhat dfferent from the other VFET-SIT given they use a new silicon carbide process?

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They were an improvement over the original VFETS's, use a Silicon Carbide process, which meant they could be made more powerful than previously, and with better technical performance (including lower distrortion). Its just a shame that SemiSouth went out of business as I'm sure it would be possible to make one pretty easily. The SIT-2 especially is a dead simple amp, its definitely in the KISS school of amp design.

many thanks to everyone for the precious infos.
I should be able to audition the SIT-2 with my Utopia, lt's see.... emh.... hear the result. If as I imagine it wil be nice, I'll buy an used SIT-2 or a new SIT-3

Right understood. I've only really tried the Audeze LCD-3 in planars, which were ok but not as nice as the HD800's. My main criteria is that headphones need to be light and comfortable so the HD800's are probably optimal for that of those I've tried.

The fact is though, is that I don't really like headphones that much, only using them when I have to! Give me a decent speaker based system any day, assuming one has plenty of space and co-operation from any family members (or business ones!). But when I do, I want them to be as close to my speaker listening experience as I can get.